The Zx Spectrum Ula- How To Design A Microcomputer -zx Design Retro Computer- -

Implement all this in an FPGA (e.g., Lattice ICE40, ECP5, or Intel MAX10) or a 5V-tolerant CPLD if you want vintage bus logic.

Enter Ferranti, a British semiconductor company. They offered the . In essence, a ULA was a pre-fabricated silicon wafer containing arrays of unconnected logic gates (AND, OR, NOT). The designer would specify a custom metal mask to connect these gates. This was cheaper than a full custom ASIC (Application-Specific Integrated Circuit) because the base silicon was generic. Implement all this in an FPGA (e

Sinclair handed engineer Richard Altwasser a seemingly impossible task: Design a computer using a single Ferranti ULA to replace 70% of the discrete logic. In essence, a ULA was a pre-fabricated silicon

+----------------+ | Z80 CPU | | (or eZ80/T80) | +-------+--------+ | +-------+--------+ | ULA/FPGA | <---> RAM (4164 or modern SRAM) +-------+--------+ <---> ROM (27C256 or flash) | +-------+--------+ | I/O devices | | (Keyboard, | | Tape, Beeper)| +----------------+ That costs money

Before diving into the design of the ZX Spectrum, we need to understand the economic landscape of early 1980s Britain. Sir Clive Sinclair’s company, Sinclair Research, operated on a philosophy of "horizontal integration"—make the product so cheap that volume destroys the competition.

: It uses the Spectrum as a template to teach the principles of designing an 8-bit microcomputer from scratch.

Traditional computer design used standard logic chips (7400 series TTL). To generate a video signal, manage DRAM refresh, scan the keyboard, and control the CPU bus, you might need 30 to 40 separate chips. That costs money, consumes power, and takes up space.